CN104479742B

CN104479742B - Biomass gas preparation system

Info

Publication number: CN104479742B
Application number: CN201410733758.6A
Authority: CN
Inventors: 刘效洲; 马培碧
Original assignee: Guangzhou Huanyu Energy Science & Technology Co ltd
Current assignee: Guangzhou Huanyu Energy Science & Technology Co ltd
Priority date: 2014-12-04
Filing date: 2014-12-04
Publication date: 2021-04-02
Anticipated expiration: 2034-12-04
Also published as: CN104479742A

Abstract

The invention discloses a biomass gas preparation system, wherein the inner space of a furnace body is divided into a gasification reaction area and a feeding and exhausting integrated area through a first sieve plate. Wherein, the feeding and exhausting integrated area is divided into a biomass feeding channel and a fuel gas collecting and discharging channel by the charging barrel. And the outer side of the feeding and exhausting integrated area is provided with a wind shell around the outer wall of the furnace body, and the wind shell is used for recycling the heat of the furnace wall of the feeding and exhausting integrated area to prepare hot air. The upper portion of wind shell is equipped with the cold wind entry, and the lower part of wind shell is equipped with the hot-air outlet, and the cold wind entry passes through pipe connection to fan, and the hot-air outlet passes through the hot-air inlet intercommunication on pipeline and the diapire of furnace body. Therefore, the cold air is preheated to be hot air in the air shell and then conveyed into the furnace body through the hot air inlet, and the hot air and the water vapor conveyed through the water vapor inlet together gasify the biomass materials accumulated in the gasification reaction zone.

Description

Biomass gas preparation system

Technical Field

The invention relates to a fuel production system, in particular to a biomass fuel production system.

Background

As is well known, fossil energy such as coal, oil, and natural gas is a non-renewable resource and is gradually exhausted in large-scale human exploitation. In addition, these fuels emit a large amount of toxic and harmful gases into the air when burned, causing serious pollution to the atmosphere. For this reason, experts in the energy field are striving to find renewable clean fuels to replace fossil energy.

The biomass fuel (BMF for short, such as agricultural and forestry waste, such as straw, sawdust, bagasse, rice chaff and the like) has the following characteristics: 1. the energy of BMF comes from the growth to natural CO₂So that the BMF has CO₂Ecological zero discharge; 2. BMF mainly burns volatile matters, has the fixed carbon content of about 15 percent, and is a typical low-carbon fuel; 3. BMF has lower sulfur content than diesel oil, only 0.05%, and SO can be realized without a desulfurizing device₂Discharging of (3); 4. the ash content of BMF is only 1.8%, which is about 1/10% of coal-based fuel, and the dust emission can reach the standard by arranging a simple dust removal device; 5. low nitrogen content of BMF, high oxygen content and less N generation during combustionO_X(ii) a 6. BMF comes from agricultural and forestry wastes, has wide and various raw material distribution, low cost and cyclic growth, is inexhaustible, and is a typical cyclic economic project.

Research and development of biomass fuel technology become one of the major hot issues in the world, and are concerned by governments and scientists of various countries in the world. The utilization of biomass energy mainly comprises 3 ways such as direct combustion, thermochemical conversion and biochemical conversion. Direct combustion of biomass has been the primary means by which biomass can be utilized in our country for a considerable period of history. Thermochemical conversion of biomass refers to the technology of gasifying, carbonizing, pyrolyzing, and liquefying biomass under certain temperatures and conditions to produce gaseous fuels, liquid fuels, and chemicals. The biochemical conversion of biomass includes biomass-biogas conversion, biomass-ethanol conversion, and the like.

Biomass gasification is a process in which biomass is used as a raw material, oxygen (air, oxygen-rich gas or pure oxygen), steam or hydrogen and the like are usually used as gasifying agents (also called gasification substances) under the action of the gasifying agents, and combustible parts in the biomass are converted into combustible gas through thermochemical reaction under high temperature conditions. The gas component generated during biomass gasification mainly comprises H₂、CH₄And CO, etc., and this combustible gas is commonly referred to as biomass gas.

In the process of biomass gasification, the gasification effect and the combustion process have an inseparable relationship, because the combustion process is the basis of biomass gasification, and the gasification is partial combustion or anoxic combustion, and the oxidation combustion process of carbon in biomass provides heat for the gasification process. In gasification reactions, the progress of other processes depends on the exothermicity of the carbon combustion stage. Thus, fundamentally, the biomass gasification process is a thermal cracking process that occurs under high temperature conditions in order to increase the production of combustible gas.

Biomass gasification technology is a widely used means of biomass energy conversion relative to other biomass utilization technologies. Its advantages include high energy conversion efficiency, simple equipment, low investment, easy operation and no limitation of region, fuel and weather. The biogas generated by the biomass gasification furnace can be used for cooking, heating and drying grains, wood and the like, and can also be used as fuel of power devices such as an internal combustion engine, a heat engine and the like, so that the biogas can be converted into electric power or power, and the grade and the use efficiency of biomass energy sources can be improved.

The gasification process of biomass is mainly performed in a gasification furnace, and the gasification reaction process is different due to different conditions such as the type of the gasification furnace, the gasification reaction conditions, the process flow, the type of the gasification agent, the properties of the raw material, the crushing particle size and the like. However, the biomass gasification process under different conditions basically comprises: c + O₂＝CO₂；CO₂+C＝2CO；H₂O+C＝CO+H₂And the like.

In general, the actual reaction process of biomass mainly comprises four parts: (1) the biomass enters the gasifier from the top of the gasifier, and after the biomass is heated to about 200-300 ℃, moisture in the biomass raw material is heated and evaporated firstly, and the final product is a dry material; (2) the biomass drying and analyzing device comprises a drying layer, a pyrolysis layer, a drying layer and a control layer, wherein dry biomass materials downwards move from the drying layer to enter the pyrolysis layer, a large amount of volatile matters in the biomass can be separated out under the action of high temperature, the action temperature is about 500-600 ℃, only residual charcoal is left after the volatile matters are separated out, and the volatile matters separated out through thermal decomposition reaction mainly comprise hydrogen, carbon monoxide, carbon dioxide, methane, tar, other hydrocarbons and the like; (3) the biomass fuel comprises a biomass layer, an oxidation layer (also called a combustion layer), wherein only charcoal remains after the biomass passes through a pyrolysis layer, and the biomass reacts violently with introduced air in the oxidation layer at the moment, releases a large amount of heat and provides heat for the reaction of other areas; (4) the reduction layer is free of oxygen, combustion products and water vapor in the oxidation layer and charcoal in the reduction layer are subjected to reduction reaction, the gases and volatile matters form combustible gases, the conversion process from solid biomass to gas fuel is completed, the reduction reaction is endothermic, the temperature is reduced to about 700-900 ℃, and the required heat mainly comes from the oxidation layer.

The gasification reaction of biomass is mainly performed in a gasification furnace, and thus the gasification furnace is a main apparatus for gasifying biomass, and can be classified into a fluidized bed gasification furnace and a fixed bed gasification furnace according to the operation mode of the gasification furnace. Wherein, in the fluidized bed gasification furnace, crushed biomass raw materials are put into the gasification furnace, a gasification agent is blown into the gasification furnace from the bottom of a grate upwards by a blower, and the gasification reaction of the fuel is completed in a boiling state. The fixed bed gasification furnace is characterized in that minced biomass raw materials are fed into the fixed bed gasification furnace from a feeding port at the top of the furnace, the materials basically carry out gasification reaction in the furnace in a layered manner, and the flow of gas generated by the reaction in the furnace is realized by a power equipment fan.

In the updraft type fixed bed gasification furnace, biomass raw materials are fed from the top of the gasification furnace, gasification agents enter the furnace from an air inlet at the bottom of the furnace body to participate in reaction, gas generated by the reaction flows from bottom to top, and finally the gas is discharged from a gas outlet at the upper part of the gasification furnace. The reaction process of the biomass sequentially comprises a drying layer, a pyrolysis layer, a reduction layer and an oxidation layer from top to bottom. Its advantages are: when the fuel gas passes through the thermal decomposition area and the drying area, the heat carried by the fuel gas is transferred to the biomass raw material for drying and thermal decomposition of the raw material, and meanwhile, the temperature of the fuel gas is reduced, and the thermal efficiency of the gasification furnace is improved; because the biomass raw material is added from the upper part of the furnace, the biogas passes through the material layer when coming out from the upper part, has a certain filtering effect on the biogas, and reduces the ash content in the biogas.

The biomass gasification boiler using air and water vapor as a gasifying agent comprises a boiler body, a grate, a fuel equalizer and a preheating pipe, wherein the boiler body consists of an inner boiler wall and an outer boiler wall sleeved on the inner boiler wall, the upper cavity of the boiler body is cylindrical, the upper cavity of the boiler body is a gasification combustion chamber, the lower cavity of the boiler body is inverted conical, the lower cavity of the boiler body is an ash falling chamber, the grate is positioned above the ash falling chamber and is arranged in the lower end of the gasification combustion chamber, and the preheating pipe is arranged at the upper end in the gasification combustion chamber and is communicated with the fuel equalizer arranged on the upper end wall of the boiler body; the biomass gasification boiler also comprises a water inlet pipe, an atomizing nozzle, an air inlet pipe, a partition plate, a hot air and water vapor mixing pipeline, a throat pipe, a secondary air pipe group and a connecting pipe; the hot air and water vapor mixing pipeline is arranged below the fire grate, the fire grate is formed by vertically and horizontally interweaving a plurality of horizontally arranged fire grate pipes, and a plurality of primary air through holes are formed in the lower half pipe wall of each fire grate pipe; be located and be equipped with airtight annular atomizing chamber on the lateral wall of the cylindrical furnace body of grate top, airtight annular atomizing chamber is direct to carry out the heat exchange through interior oven and gasification combustion chamber, the baffle sets up in inclosed annular atomizing chamber, the airtight annular atomizing chamber intercommunication of air admission pipe and baffle one side, the airtight annular atomizing chamber intercommunication of atomizing nozzle and baffle opposite side is passed through to the inlet tube, the export of hot-air steam mixing pipeline and the airtight annular atomizing chamber intercommunication between baffle and the atomizing nozzle, each grate pipe is through hot-air steam mixing pipeline and airtight annular atomizing chamber intercommunication. However, the biomass gasification boiler using air and water vapor as gasifying agents has the following disadvantages or shortcomings: (1) the tar content in the directly prepared biomass gas is high, if the biomass gas is not filtered, the subsequent use performance of the gas is seriously influenced, and the biomass gasification boiler patent application does not disclose or suggest how to effectively reduce the tar content in the biomass gas; (2) the furnace wall at the middle upper part of the biomass gasification boiler does not adopt a waste heat recovery structure, so that a part of heat energy is wasted, and if the part of heat energy can be used for preheating air or water, the energy is saved and the environment is protected; (3) the biomass feeding channel and the biomass gas discharging channel of the biomass gasification boiler are not physically separated, which is not beneficial to respectively controlling feeding and discharging; (4) the water vapor preparation method of the biomass gasification boiler is that cold water in the water pipe is directly sprayed to the high-temperature furnace wall through the atomizing nozzle to be heated into water vapor which is directly supplied to the gasification furnace, so that the prepared water vapor inevitably contains a certain amount of atomized water drops, which is not beneficial to the subsequent reduction reaction in the gasification furnace; (5) the primary air preparation method of the biomass gasification boiler is that cold air is directly sent into the closed annular atomization cavity to be mixed with water vapor to prepare hot air and water vapor mixed gas, and then the hot air and water vapor mixed gas is supplied into the gasification furnace, so that the content of atomized water drops in the water vapor is further increased.

Also as disclosed in chinese patent application publication No. 102643676a, a method for pyrolysis and gasification of biomass by gas-fired reflow combustion and self-heating, the biomass is in a pyrolysis and gasification furnace, air and steam are used as gasifying agents to perform pyrolysis and gasification reactions, the waste heat of the produced gas is used to prepare superheated steam from the steam produced by an evaporator to supplement heat for the furnace, and the gas produced in the reflow part enters the furnace to burn to provide heat for the gasification reactions, and high-temperature cracking is used to remove tar, thereby ensuring that the gasification furnace is wholly in a high-temperature atmosphere, and ensuring that the gasification process of the biological pyrolytic carbon and the cracking process of the tar tend to be complete. However, the fuel gas reflux combustion self-heating biomass pyrolysis gasification method has the following disadvantages or shortcomings: (1) it does not disclose or suggest how to effectively reduce tar content in biomass gas; (2) the used air is not preheated by using the waste heat of the boiler; (3) the water vapor is prepared by adopting a special evaporator; (4) and the furnace wall of the furnace is not provided with a waste heat recovery structure, so that a part of heat energy is wasted.

Therefore, the biomass gas preparation system capable of fully improving the energy utilization rate is a problem which needs to be solved urgently in the industry.

Disclosure of Invention

The invention aims to provide a biomass gas preparation system which can fully improve the energy utilization rate and improve the quality of biomass gas.

According to an aspect of the present invention, there is provided a biomass fuel gas production system including: updraft type fixed bed gasification furnace, updraft type fixed bed gasification furnace include the furnace body, and the inner space of furnace body is separated for the gasification reaction zone that is arranged in the lower part and is used for piling up the living beings bed of material and is located the feeding exhaust of gasification reaction zone top and synthesize the district through first sieve, and wherein, the roof of furnace body is equipped with the living beings feed inlet, and the diapire of furnace body is equipped with steam inlet and hot-air inlet, and first sieve is equipped with the living beings discharge gate. The feeding and exhausting integrated area is divided into a biomass feeding channel positioned in the center and a fuel gas collecting and discharging channel arranged around the biomass feeding channel through a charging barrel, and a fuel gas outlet is formed in the top wall of the furnace body and at the top of the fuel gas collecting and discharging channel; one end of the biomass feeding channel is communicated with a biomass feeding hole on the top wall of the furnace body, the other end of the biomass feeding channel is communicated with a biomass discharging hole on the first sieve plate, and the fuel gas collecting and discharging channel is positioned in a space defined by the upper surface of the first sieve plate, the outer surface of the charging barrel and the inner surface of the furnace body; and the outer side of the feeding and exhausting integrated area is provided with an air shell around the outer wall of the furnace body, the air shell is used for recycling furnace wall heat of the feeding and exhausting integrated area to prepare hot air, wherein the upper part of the air shell is provided with a cold air inlet, the lower part of the air shell is provided with a hot air outlet, the cold air inlet is connected to a fan through a pipeline, and the hot air outlet is communicated with a hot air inlet on the bottom wall of the furnace body through a pipeline, so that the cold air is preheated into hot air (100-200 ℃, for example, about 150 ℃) in the air shell and then is conveyed into the furnace body through the hot air inlet to gasify biomass materials accumulated in the gasification reaction area together with water vapor conveyed through the water vapor inlet.

Preferably, a heat exchange coil can be arranged in the fuel gas collecting and discharging channel for recycling heat in the biomass fuel gas to prepare water vapor at one time. Wherein, cold water is heated into a steam-water mixture at about 100 ℃ in the heat exchange coil, and the steam dryness is about 60%.

Preferably, a water jacket may be provided around the outer wall of the furnace body at the outer side of the gasification reaction zone for recycling the heat of the furnace wall of the gasification reaction zone to secondarily produce water vapor. The steam-water mixture from the heat exchange coil is further heated in the water jacket to improve the steam temperature and dryness, meanwhile, the return water from the steam-water separator is circularly heated in the water jacket to be steam so as to save water resources, and in addition, the amount of the return water in the water jacket is controlled to be less than 20% of the volume of the water jacket so as to avoid influencing the normal operation of the system.

Preferably, the biomass fuel gas preparation system can be further provided with a steam-water separator for removing liquid water in the water vapor to prepare the water vapor for three times. The steam-water separator is a conventional steam-water separator, and the working principle is as follows: the steam containing water enters the steam-water separator and moves in the steam-water separator in a centrifugal downward inclined mode, and the entrained water is separated out due to the fact that the speed is reduced; the separated liquid stream is discharged through a trap and the dry, clean steam is discharged from the separator outlet.

Optionally, the upper part of the water jacket is provided with a water inlet and a steam outlet, and the lower part of the water jacket is provided with a return water inlet; one end of the heat exchange coil is connected with the water pump, and the other end of the heat exchange coil is communicated with the water inlet of the water jacket, so that the water vapor prepared for the first time is conveyed into the water jacket for the second time preparation.

Optionally, the steam-water separator is provided with a steam-water inlet, a backwater outlet and a steam outlet; the steam-water inlet is communicated with the steam-water outlet of the water jacket through a pipeline so as to introduce the steam-water mixture in the water jacket into the steam-water separator to separate high-purity steam; the backwater outlet is communicated with the backwater inlet of the water jacket through a pipeline and is used for feeding liquid water separated from the steam-water separator into the water jacket for heating so as to circularly prepare water vapor; the steam outlet is communicated with the steam inlet on the bottom wall of the furnace body through a pipeline.

Optionally, a ceramic ball filtering layer can be arranged above the first sieve plate and used for filtering tar in the biomass gas at the first stage, and the heat exchange coil is arranged above the ceramic ball filtering layer in the gas collecting and discharging channel.

Optionally, the biomass gas preparation system may further include a cyclone dust collector, the gas outlet is connected to the cyclone dust collector through a pipeline to remove ash in the biomass gas, the cyclone dust collector includes a first-stage gas inlet, a first-stage gas outlet and a discharger, the first-stage gas inlet is arranged along a tangential direction of a body of the cyclone dust collector to enable the gas to flow in a spiral manner inside the cyclone dust collector, the first-stage gas outlet is arranged at the top of the body of the cyclone dust collector, and the discharger is arranged at the bottom of the body of the cyclone dust collector to collect the ash.

Optionally, the biomass gas preparation system may further comprise a secondary filter device, the secondary filter device is provided with a secondary gas inlet and a secondary gas outlet, the secondary gas inlet is connected to the primary gas outlet of the cyclone dust collector through a pipeline, and the secondary gas outlet outputs clean biomass gas.

Optionally, the inside of the secondary filter device may include a transition ash removal chamber located at the lower part and separated by the second sieve plate and a filter area located above the transition ash removal chamber, the filter area includes a first filter chamber and a second filter chamber separated by the partition plate, the middle lower parts of the first filter chamber and the second filter chamber are both provided with a sawdust filter layer, the secondary gas inlet is arranged at the top of the first filter chamber, and the secondary gas outlet is arranged at the top of the second filter chamber.

Optionally, a material distribution cone is arranged below the biomass discharge port and used for uniformly dispersing the biomass material to the gasification reaction zone.

Preferably, a rotary driving device is further arranged for driving the material distribution cone to rotate, so that the biomass material is more uniformly dispersed.

Optionally, the furnace body of the updraft fixed bed gasification furnace is cylindrical, the first sieve plate is annular, and a plurality of through holes are formed in the first sieve plate.

Optionally, a third sieve plate is further arranged on the top of the sawdust filtering layer in the second filtering chamber to prevent the produced clean biomass fuel gas from mixing into sawdust.

Optionally, the biomass feed inlet is arranged in the center of the top wall of the furnace body, and the biomass discharge outlet is arranged in the center of the first sieve plate.

Alternatively, the lower part of the updraft fixed bed gasification furnace is provided with an ash collecting chamber, the ash collecting chamber and the gasification reaction zone are separated by a grate, at least one water vapor pipe and at least one hot air pipe are arranged below the grate, the water vapor pipe comprises a plurality of water vapor outlets, the hot air pipe comprises a plurality of hot air outlets, and the water vapor pipe and the hot air pipe are arranged in a cross shape or a lantern ring shape.

The invention has the beneficial effects that: (1) the air shell is arranged for preheating air, and the heat exchange coil and the water jacket are arranged for heating water vapor, so that the utilization rate of biomass energy is fully improved; (2) the high-purity water vapor is prepared by adopting a three-stage process, so that the reaction efficiency of the biomass gasification furnace is fully improved; (3) and a secondary tar filtering process and a cyclone dust removal process are adopted, so that the quality of the clean biomass fuel is fully improved.

Drawings

FIG. 1 shows a schematic of a biomass fuel gas production system of the present invention.

Detailed Description

Referring to fig. 1, according to an embodiment of the present invention, a biomass fuel gas preparation system includes: the gasification system comprises an updraft fixed bed gasification furnace 100, a steam-water separator 300, a cyclone dust removal device 500 and a secondary filtering device 700.

The updraft fixed bed gasification furnace 100 includes a furnace body 110 whose inner space is partitioned into a gasification reaction zone 150 for stacking a biomass material layer at a middle lower portion and a feed and exhaust integrated zone (not numbered) above the gasification reaction zone 130 by a first sieve plate 120. Wherein, the top wall of furnace body 110 is equipped with living beings feed inlet 115, and the diapire of furnace body 110 is equipped with steam inlet 116 and hot-air inlet 117.

In this non-limiting embodiment, the furnace body 110 of the updraft fixed bed gasification furnace 100 is cylindrical, and the first sieve plate 120 is annular and has a plurality of through holes opened therein. The biomass inlet 115 is disposed at the center of the top wall of the furnace body 110, and the biomass outlet 125 is disposed at the center of the first sieve plate 120.

The feed and exhaust integration zone is divided by the cartridge 150 into a centrally located biomass feed channel 160 and a fuel gas collection and exhaust channel 170 disposed around the biomass feed channel 160. A gas outlet 177 is formed at the top of the gas collecting and discharging passage 170 on the top wall of the furnace body 110. One end of the biomass feed channel 160 is communicated with the biomass feed inlet 115 on the top wall of the furnace body, and the other end of the biomass feed channel 160 is communicated with the biomass discharge outlet 125 on the first sieve plate 120. The gas collecting and discharging passage 170 is located in a space surrounded by the upper surface of the first sieve plate 120, the outer surface of the barrel 150, and the inner surface of the furnace body 110.

The heat exchange coil 140 is arranged in the gas collection and discharge channel 170 and is used for recycling heat in the biomass gas to prepare water vapor at one time. Cold water from water pump 900 is heated in heat exchange coil 140 to a steam-water mixture of about 100 degrees celsius, with a steam quality of about 60%.

In the gas collecting and discharging channel 170, a ceramic ball filtering layer 400 is disposed above the first sieve plate 120 and below the heat exchanging coil 140 for primarily filtering tar in the biomass gas.

In this non-limiting embodiment, the updraft fixed bed gasification furnace 100 is further provided with a wind housing 180 surrounding along the outer wall of the furnace body 110 outside the feed and exhaust integrated zone, for recycling furnace wall heat of the feed and exhaust integrated zone to produce hot air. The upper portion of the air casing 180 is provided with a cold air inlet 185, the lower portion of the air casing 180 is provided with a hot air outlet 186, the cold air inlet 185 is connected to the fan 800 through a pipeline, and the hot air outlet 186 is communicated with the hot air inlet 117 on the bottom wall of the furnace body 110 through a pipeline.

In this non-limiting embodiment, the updraft fixed bed gasification furnace 100 is further provided with a water jacket 190 surrounding along the outer wall of the furnace body 110 at the outside of the gasification reaction zone 130 for recycling furnace wall heat of the gasification reaction zone to secondarily produce water vapor. The steam-water mixture from the heat exchange coil 140 is further heated in the water jacket 190 to increase the steam temperature and dryness, while the return water from the steam-water separator 300 is circularly heated in the water jacket 190 to steam to save water resources.

The upper part of the water jacket 190 is provided with a water inlet 191 and a steam outlet 192, and the lower part of the water jacket 190 is provided with a water return inlet 193. One end of the heat exchange coil 140 is connected to the water pump 900 and the other end is communicated with the water inlet 191 of the water jacket 190, so as to convey the water vapor prepared in the first time into the water jacket 190 for the second time preparation.

In this non-limiting embodiment, the biomass fuel gas preparation system is further provided with a steam-water separator 300 for removing liquid water from the water vapor to prepare water vapor three times. The steam-water separator 300 is provided with a steam-water inlet 301, a steam outlet 302 and a return water outlet 303. The steam-water inlet 301 is communicated with the steam-water outlet 192 of the water jacket 190 through a pipeline so as to introduce the steam-water mixture in the water jacket into the steam-water separator to separate high-purity steam. The backwater outlet 303 is communicated with the backwater inlet 193 of the water jacket 190 through a pipeline and is used for feeding liquid water separated from the steam-water separator into the water jacket for heating so as to circularly prepare water vapor. The steam outlet 302 is in communication with the steam inlet 116 on the bottom wall of the furnace body 110 through a pipeline.

Thus, the cool air from the blower fan 800 is preheated to hot air of about 150 degrees celsius in the blower case 180, and then delivered into the furnace body 110 through the hot air inlet 117. The cold water from the water pump 900 is heated in the heat exchange coil 140 to a steam-water mixture of about 100 ℃, the steam-water mixture is further heated in the water jacket 190 to increase the steam temperature and dryness, and then the steam-water mixture enters the steam-water separator 300 to separate high-purity steam. The prepared hot air and steam are separately delivered to the gasification reaction zone 130 to gasify the biomass materials 200 accumulated therein. The biomass gas generated by gasification enters the gas collecting and discharging channel 170 through the first sieve plate 120, the biomass gas firstly passes through the ceramic ball filtering layer 400 to perform primary tar filtering, then exchanges heat with cold water in the heat exchange coil 140, and finally the biomass gas at about 110 ℃ is discharged out of the updraft type fixed bed gasification furnace 100 from the gas outlet 177.

As an alternative embodiment, the biomass fuel gas preparation system further includes a cyclone dust removing device 500. The gas outlet 177 of the updraft fixed bed gasification furnace 100 is connected to the cyclone dust removing device 500 through a pipeline to remove ash in the biomass gas. The cyclone dust removal device 500 comprises a primary fuel gas inlet 501, a primary fuel gas outlet 502 and a blanking device 505. The primary combustion gas inlet 501 is provided along a tangential direction of a body of the cyclone device 500 (in this embodiment, the body is approximately cylindrical) so that the combustion gas flows spirally inside the cyclone device 500. The primary gas outlet 502 is provided at the top of the body of the cyclone dust removing device 500. The downer 505 is disposed at the bottom of the body of the cyclone device 500 for collecting ash.

As an alternative embodiment, the biomass fuel gas preparation system further comprises a secondary filtration device 700. The secondary filter device 700 is provided with a secondary gas inlet 701 and a secondary gas outlet 702. The secondary gas inlet 701 is connected to the primary gas outlet 502 of the cyclone dust collector through a pipeline, and the secondary gas outlet 702 outputs clean biomass gas. The interior of the secondary filter device 700 includes a lower transitional ash removal chamber 730 divided by a second screen deck 720 and a filtering zone (not numbered) above the transitional ash removal chamber. The filtering area comprises a first filtering chamber 760 and a second filtering chamber 770 which are separated by a partition plate 750, and the middle lower parts of the first filtering chamber 760 and the second filtering chamber 770 are respectively provided with a sawdust filtering layer 780. The secondary fuel gas inlet 701 is disposed at the top of the first filter chamber 760, and the secondary fuel gas outlet 702 is disposed at the top of the second filter chamber 770. A third sieve plate 790 is further disposed on the top of the sawdust filter layer 780 in the second filter chamber 770 to prevent the prepared clean biomass fuel gas from mixing with sawdust.

As an alternative embodiment, a material distribution cone 166 is disposed below the biomass discharging port 125 for uniformly distributing the biomass material to the gasification reaction zone 130, and a rotary driving device (not shown) is further disposed for driving the material distribution cone 166 to rotate, so that the biomass material is more uniformly distributed.

As an alternative embodiment, the lower portion of the updraft fixed bed gasification furnace is provided with an ash collection chamber (not shown), the ash collection chamber is separated from the gasification reaction zone by a grate (not shown), a plurality of water vapor pipes and a plurality of hot air pipes are arranged below the grate, the water vapor pipes comprise a plurality of water vapor outlets, the hot air pipes comprise a plurality of hot air outlets, and the water vapor pipes and the hot air pipes are arranged in a cross shape.

Although preferred embodiments of the present invention have been described in detail herein, it is to be understood that this invention is not limited to the precise construction herein shown and described in detail, and that other modifications and variations may be effected by one skilled in the art without departing from the spirit and scope of the invention. For example, the steam produced in the first stage or the steam produced in the second stage may be supplied directly to the gasification reaction zone without using the next stage steam production process. In addition, the temperature or pressure of various parts of the system can be properly selected within the range disclosed in the present invention according to the specific use condition.

Claims

1. A biomass gas production system, comprising:

the updraft type fixed bed gasification furnace comprises a furnace body, wherein the inner space of the furnace body is divided into a gasification reaction zone positioned at the middle lower part and used for accumulating a biomass material layer and a feeding and exhausting comprehensive zone positioned above the gasification reaction zone through a first sieve plate, a biomass feeding port is arranged on the top wall of the furnace body, a water vapor inlet and a hot air inlet are arranged on the bottom wall of the furnace body, and a biomass discharging port is arranged on the first sieve plate;

the method is characterized in that:

the feeding and exhausting integrated area is divided into a biomass feeding channel positioned in the center and a fuel gas collecting and exhausting channel arranged around the biomass feeding channel through a charging barrel, and a fuel gas outlet is formed in the top wall of the furnace body and at the top of the fuel gas collecting and exhausting channel;

one end of the biomass feeding channel is communicated with the biomass feeding hole in the top wall of the furnace body, the other end of the biomass feeding channel is communicated with the biomass discharging hole in the first sieve plate, and the fuel gas collecting and discharging channel is positioned in a space defined by the upper surface of the first sieve plate, the outer surface of the charging barrel and the inner surface of the furnace body; a material distribution cone is arranged below the biomass discharge port and used for uniformly distributing the biomass materials to the gasification reaction zone, and a rotary driving device is further arranged and used for driving the material distribution cone to rotate, so that the biomass materials are more uniformly distributed;

an air shell is arranged on the outer side of the feeding and exhausting integrated area along the outer wall of the furnace body in a surrounding mode and used for recycling furnace wall heat of the feeding and exhausting integrated area to prepare hot air, wherein a cold air inlet is formed in the upper portion of the air shell, a hot air outlet is formed in the lower portion of the air shell, the cold air inlet is connected to a fan through a pipeline, the hot air outlet is communicated with the hot air inlet in the bottom wall of the furnace body through a pipeline, and therefore the cold air is preheated into hot air in the air shell and then conveyed into the furnace body through the hot air inlet to enable biomass materials accumulated in the gasification reaction area to be gasified together with water vapor conveyed through the water vapor inlet;

the gas collection and discharge channel is internally provided with a heat exchange coil for recycling heat in the biomass gas to prepare water vapor for the first time, the outer side of the gasification reaction zone is surrounded by a water jacket along the outer wall of the furnace body for recycling furnace wall heat of the gasification reaction zone to prepare water vapor for the second time, a ceramic ball filter layer is arranged above the first sieve plate and used for filtering tar in the biomass gas for the first time, and the heat exchange coil is arranged above the ceramic ball filter layer in the gas collection and discharge channel;

the biomass fuel gas preparation system further comprises:

the gas outlet is connected to the cyclone dust removal device through a pipeline so as to remove ash in biomass gas, the cyclone dust removal device comprises a primary gas inlet, a primary gas outlet and a feeder, the primary gas inlet is arranged along the tangential direction of a body of the cyclone dust removal device so that gas can spirally flow in the cyclone dust removal device, the primary gas outlet is arranged at the top of the body of the cyclone dust removal device, and the feeder is arranged at the bottom of the body of the cyclone dust removal device and is used for collecting ash; and

the secondary filter device is provided with a secondary fuel gas inlet and a secondary fuel gas outlet, the secondary fuel gas inlet is connected to the primary fuel gas outlet of the cyclone dust removal device through a pipeline, and the secondary fuel gas outlet outputs clean biomass fuel gas;

the secondary filter device comprises a transition ash removal cavity and a filter area, wherein the transition ash removal cavity is located at the lower part and is separated by a second sieve plate, the filter area is located above the transition ash removal cavity, the filter area comprises a first filter cavity and a second filter cavity, the first filter cavity and the second filter cavity are separated by a partition plate, saw dust filter layers are arranged at the middle lower parts of the first filter cavity and the second filter cavity, a secondary fuel gas inlet is formed in the top of the first filter cavity, and a secondary fuel gas outlet is formed in the top of the second filter cavity; a third sieve plate is further arranged on the top of the sawdust filtering layer in the second filtering cavity to prevent sawdust from being mixed into the prepared clean biomass gas;

the lower part of the updraft type fixed bed gasification furnace is provided with an ash collecting chamber, the ash collecting chamber is separated from the gasification reaction zone through a grate, at least one water vapor pipe and at least one hot air pipe are arranged below the grate, the water vapor pipe comprises a plurality of water vapor outlets, the hot air pipe comprises a plurality of hot air outlets, and the water vapor pipe and the hot air pipe are arranged in a cross shape or a lantern ring shape.

2. The biomass gas preparation system according to claim 1, further comprising a steam-water separator for removing liquid water from the water vapor to prepare water vapor three times.

3. The biomass gas preparation system according to claim 2, wherein the upper part of the water jacket is provided with a water inlet and a steam-water outlet, and the lower part of the water jacket is provided with a return water inlet; one end of the heat exchange coil is connected with a water pump, and the other end of the heat exchange coil is communicated with the water inlet of the water jacket, so that the water vapor prepared for the first time is conveyed into the water jacket for the second time preparation.

4. The biomass gas preparation system according to claim 3, wherein the steam-water separator is provided with a steam-water inlet, a return water outlet and a steam outlet; the steam-water inlet is communicated with the steam-water outlet of the water jacket through a pipeline so as to introduce the steam-water mixture in the water jacket into the steam-water separator to separate high-purity steam; the backwater outlet is communicated with the backwater inlet of the water jacket through a pipeline and is used for feeding liquid water separated from the steam-water separator into the water jacket for heating so as to circularly prepare water vapor; the steam outlet is communicated with the water steam inlet on the bottom wall of the furnace body through a pipeline.